Sensory implants are used for monitoring physiological parameters of patients, such as for measuring blood pressure in a cardiac chamber. Various types of sensory implants and associated methods are known in the art. For example, U.S. Patent Application Publication 2007/0261496, whose disclosure is incorporated herein by reference, describes biological fluid device that comprises a pressure sensor. The pressure sensor comprises a compressible container, the compression of which is indicative of the pressure, and is capable of wireless communication.
U.S. Pat. No. 7,335,161, whose disclosure is incorporated herein by reference, describes an implantable cardiac device that is configured and programmed to collect blood pressure waveforms from one or more implantable pressure sensors. Techniques are described for extracting features and reducing noise in the pressure waveforms by averaging waveforms which are aligned with a detected cardiac cycle. Noise can also be reduced by gating and calibration functions performed in accordance with other sensor data.
U.S. Pat. No. 5,942,692, whose disclosure is incorporated herein by reference, describes a capacitive pressure sensor that includes a chamber coupled to a region whose pressure is to be determined. The sensor includes a conductive flexible diaphragm and a pair of electrodes, each defining a capacitance with the diaphragm. Variations in pressure in the chamber cause deflection of the diaphragm which in turn causes variation in the capacitances. A processing circuit applies an excitation signal to the capacitances and couples the capacitances to inductive elements. A current through the inductive elements is detected to determine the difference in the sensor capacitances and, therefore, the deflection of the diaphragm and the pressure in the chamber.
U.S. Patent Application Publication 2007/0142727, whose disclosure is incorporated herein by reference, describes a cardiovascular pressure data analyzing system having one or more implanted pressure sensors, an implanted communication device in wireless communication with the sensor and an external data processing unit adapted to use real-time barometric data to calibrate un-calibrated pressure data received from the communication device. The external data processing unit can be portable, is in communication with a remote database to transfer the calibrated pressure data to the remote database, and is capable of providing reprogramming information to the communication device. A method for analyzing pressure data includes gathering pressure data from an implanted pressure sensor in a human body, retrieving the pressure data through a communication device implanted in the human body, transmitting pressure data from the communication device to an external data processing unit, and calibrating the pressure data at the external processing unit to compensate for inherent characteristics of the sensor.
U.S. Patent Application Publication 2011/0160560, whose disclosure is incorporated herein by reference, describes an implantable pressure sensor system having a sensor assembly configured and adapted to measure pressure in a volume. The sensor assembly includes at least a first MEMS pressure sensor, an application-specific integrated circuit (ASIC) having memory means, temperature compensation system, drift compensation system, and power supply means for powering the sensor assembly. The first MEMS pressure sensor has a pressure sensing element that is responsive to exposed pressure, the pressure sensing element being adapted to generate a pressure sensor signal representative of the exposed pressure. The temperature compensation system is adapted to correct for temperature induced variations in the pressure sensor signal, and the drift compensation system is adapted to correct for pressure and temperature induced pressure sensor signal drift.